Help me understand an exercise bike

Lyndon Littlefair, exercise specialist for Ambition Fitness, the UK's leading independent personal training company, replies: There are two main variables with an exercise bike, 1) RPM, which is basically speed, and 2) resistance. All bike programmes from interval to hill, race to random are simply a combination of these two variables.
Exercise bikes can provide a number of benefits if you use the right combinations of these two variables for you.
If you are more interested in increasing muscle strength and muscle co-ordination, you should look to use a lower RPM combined with high resistance, such as the peak intensity of hill or interval programme modes.
If you are interested in burning fat and increasing the work load on the cardiovascular system, then a faster speed (RPM) and a low resistance, for example the race or competitive modes, would be appropriate. These types of programmes decrease the load on the legs, which means you can sustain momentum for longer, avoiding leg fatigue. This helps to develop the fast twitch muscle fibres, which in turn will develop even greater speed.
Generally, bike programmes will help you to progressively overload your body, speeding up the metabolism and fat burning potential. You will burn more calories by using a combination of variables (RPM and resistance), rather than just working flat out for a number of minutes. However, the ideal situation to accomplish both a cardiovascular and muscle workout would be a combination of a fast speed with a high resistance, but remember it's impossible to do this for lengthy periods of time.
These are not the only benefits bike modes can provide. They do a lot to elevate boredom and you never know, the race programme just might inspire your natural competitive streak!